In Quantum Field Theory (QFT), mass is a fundamental property associated with particles. In this framework, particles are described as excitations or quanta of underlying quantum fields that permeate all of space.
According to QFT, each type of particle corresponds to a specific quantum field, such as the electron field, the photon field, or the Higgs field. The interaction and behavior of these fields are described mathematically through a Lagrangian density, which governs the dynamics of the fields and their interactions.
In this context, the mass of a particle is intimately related to how the corresponding field interacts with the Higgs field. The Higgs field is a fundamental field in the Standard Model of particle physics, which is a widely accepted theory describing the fundamental particles and their interactions.
When particles interact with the Higgs field, they acquire mass through a process known as the Higgs mechanism. The Higgs mechanism involves spontaneous symmetry breaking, where the Higgs field settles into a non-zero vacuum expectation value. This vacuum expectation value causes some of the particles, specifically the gauge bosons (such as the W and Z bosons) and fermions (such as quarks and leptons), to acquire mass.
The mass of a particle in QFT affects its behavior and properties. For example, particles with larger masses tend to have slower speeds and shorter wavelengths associated with their wave-like behavior. Additionally, the mass influences the energy-momentum relationship of a particle through Einstein's famous equation, E=mc², where E is the energy, m is the mass, and c is the speed of light.
It's important to note that mass in QFT is a more nuanced concept compared to classical mechanics. In QFT, mass can be influenced by interactions with other fields, and it can even be renormalized due to quantum effects. Nonetheless, the Higgs mechanism provides a crucial understanding of how particles acquire mass within the framework of QFT.